LOX‐Induced Lipid Peroxidation Mechanism Responsible for the Detrimental Effect of Marine Diatoms on Zooplankton Grazers

Abstract

Some marine diatoms negatively affect the reproduction of dominant zooplankton grazers such as copepods, thus compromising the transfer of energy through the marine food chains. In this paper, the metabolic mechanism that leads to diatom-induced toxicity is investigated in three bloom-forming microalgae. We show that copepod dysfunctions can be induced by highly reactive oxygen species (hROS) and a blended mixture of diatom products, including fatty acid hydroperoxides (FAHs); these compounds display teratogenic and proapoptotic properties. The process is triggered by the early onset of lipoxygenase activities that elicit the synthesis of species-specific products, the basic structures of which were established (1-20); these compounds boost oxidative stress by massive lipid peroxidation. Our study might explain past laboratory and field results showing how diatoms damage zooplankton grazers even in the absence of polyunsaturated aldehydes, a class of molecules that has been formerly implicated in mediating the toxic activity of diatoms on copepods.

Effect of food concentration and type of diet on Acartia survival and naupliar development

“…It is now well illustrated that not all diatom species per se are toxic, but even taxa lacking toxic metabolites can be insufficient to support copepod recruitment and development in mono-diet (Jones and Flynn 2005). While defence chemicals of diatoms can be diverse (Fontana et al 2007) and widely present (Wichard et al 2005) there are obviously species that lack the detrimental effects originally presumed for the entire taxon, and among these can be adequate and high quality food sources for copepods.…”

The biogeochemistry of lipid derived infochemical signals in the ocean

“…However, octanol water partition coefficients appear to inaccurately predict retention times of compounds with epoxy groups; the RT logP calculated for the epoxy acid C20:4 standard was 0.68 minutes earlier than observed. In the future, hydroxy epoxy acids could be 165 isolated from Skeletonmena pseudocostatum, Skeletonmena marinoi, Leptocylindrus diatoms and/or Pseudeonitzchia delicatissimia and used as authentic standards d'Ippolito et al, 2009;Fontana et al, 2007;.…”

“…Oxylipin profiling of diatom cultures has already revealed a large diversity of NVOs molecules d'Ippolito et al, 2005;d'Ippolito et al, 2009;Fontana et al, 2007;Pohnert, 2002) . However, the bioactivities of these compounds outside of copepod grazing are poorly understood and we know very little about their diversity in the marine environment with field studies only reporting summed NVO concentrations.…”

Aldehyde-encapsulating liposomes impair marine grazer survivorship

“…After 24·h of acclimatization, couples were transferred to new crystallizing dishes containing 60·ml of 0.22·m filtered seawater and the dinoflagellate Prorocentrum minimum Pavillard (Sciller) at a final concentration of 8000·cells·ml -1 . This microalga was used as the copepod food source in our liposome experiments since it does not produce aldehydes or other oxylipins (Fontana et al, 2007).…”

“…This insidious mechanism, which does not deter the herbivore from feeding but impairs its recruitment, will restrain the cohort size of the next generation. The compounds responsible for reduced hatching success and abnormal larval development in these small crustaceans are several oxylipins, products of the enzymatic oxidation of fatty acids, which include polyunsaturated aldehydes (PUAs) as well as fatty acid hydroxides, epoxy alcohols, hydroperoxides and reactive oxygen species (ROS) (Fontana et al, 2007). These compounds are not constitutively present in the cells but are only produced when the cell is damaged as would occur during grazing (Pohnert, 2000).…”